Jacobson flare

[Short and Sweet]

I have just completed an initial Grade 1 test where the ATO demonstrated the "Jacobson approach and flare". Just wondering if anyone is teaching this new approach? How are you teaching/explaining it and is it successful with students?

[Teroc]

Whats this ?
A new way to prevent me from touch and touch and touch and go ?

Tell all...

Cheers
Teroc

[Ace on Base]

Good ol' Jacobson...... Was just thinking to myself the other day, Quietly with a beer in my hand, I wonder how long before someone posts a thread about Mr Jacobsons landing technique??

Mighty good technique to teach provided its taught correctly!!

Put it this way, It saved many chineese students rsole in Western Australia!!

Will dig up some stuff, and then post the way I see it when I aint so tired, and seeing X - eyed!!

Regards

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"Keep Smilin' Sunshiners!!"

[Meeb]

But it sure is not a 'new' technique. It was so interesting I have forgotten it, anyone care to expand, or is it just point n power re-jigged?

[This message has been edited by Meeb (edited 15 December 1999).]

[No Cigar]

Excuse my ignorance, but what is a Jacobson Flare???

[Short and Sweet]

A Capt Jacobson of an Aust Airline has mathematically (sine, cos, tan etc)worked out an equation to give you the exact height at which to flare. It takes all the guess work out of when to round out and flare.

Ace on Base correct me if I'm wrong but you hold a constant angle of approach using runway aspect not a constant aiming point. As your touchdown point passes under the nose cowling (as you are looking forward) that is the time at which to close the throttle and flare. According to my ATO it is approx 100 feet for most light aircraft (C152, 172, 182). No rounding out and hoping it doesn't float. It supposedly works every time and for all types of landings (flapless, glide, short field).

I can understand the mathematical concept but it is the explaining and teaching, having taught the aiming point technique for so long, that I am curious as to how others teach it.

[de La Valette]

For sixty years, countless thousands of pilots have landed their aircraft au natural. Suddenly a guru appears who says you have got it all wrong. The look-see technique described is just mathematical mumbo-jumbo and a re-invention of the wheel.

[squeakmail]

I'm idly curious to know...if the Wright Brothers did their bit in 1903 and we are told that people have being doing it au natural for sixty years - what did they do from 1903 to 1933? (The one's that didn't crash, that is).

[Swamp]

I have to agree with squeakmail.

If nobody ever dared to be innovative and repressed the pioneering spirit then I would be going to work every day on horseback.

Dare to be different de La Valette.

The Jacobson flare is a mathematial way of flying an approach. It almost makes sense. At the moment we almost use the "force" every time we flare. Surely it makes more sense to use a method that takes out the guesswork?

However, it is too late for some of us...

[Black Jake]

Closing the throttle and flaring a light aircraft at 100 feet? Unless you can afford a hefty maintenance bill I would recommend you go back and check your sums!

[Genghis the Engineer]

Possibly somebody somewhere initiates the roundout and calls that a flare.

That said, 100 feet sounds pretty high to initiate the roundout in most light aircraft.

[Wing & Prayer]

Having taught and seen the "Jacobson Flare" in action, I recall a friend asking a instructor at one of the major IFR training schools if they taught the "Jacobson Flare". The reply.... "Nope, we just land".... that about sums it up. Jacobson relies on flying a constant angle final approach to a nominated aiming point with a stable path descent. Jacobson clearly states to hold the aiming point constant on finals using a "cut off angle" as the determining factor for the flare. A supposed glideslope for VFR pilots.... That's about all I can remember, like Ace, I'll see if I can dig up some further info.

[de La Valette]

I can see it now. Ab-initio on final muttering "Must do the Jacobson Flare -repeat - Must do the....Oh sh**t ! ..WATCH IT BLOGGS YER BLOODY IDIOT. TRYING TO KILL ME OR WHAT?

Sorry Sir - Can I do the Jacobson flare off a bounced landing? And what if I balloon with a gust. Can I do the Jacobson flare off that too?

Watch it chaps, it's turning into yet another cottage industry - just like CRM.

[BEagle]

dlV - how right you are!! Didn't someone once say "Keep It Simple, Stupid!!"

[Capt Homesick]

dlV, BEagle, this time I fully agree with you. The jacobson flare may be very interesting, but I think it would only add to the student's confusion. Most of them are confused enough!

[Sensible]

Does one use the Jacobson flare technique on the first second or third bounce ?

[Checkboard]

Taken from Aviation Safety Digest 134

A flare for landing

Captain David Jacobson is a training Captain with Australian Airlines and is a Grade 1 Instructor at the RAAF Point Cook Flying Club. His system sounds complicated but in reality is delightfully simple. It works for little aircraft too.

Of all the manoeuvres performed in fixed-wing aircraft, the landing flare is an enigma. It is critical to the safe and satisfactory conclusion of a flight and yet, despite international research, remains more an art than a science. The way the pilot judges the flare is still not fully understood.

Student pilots and experienced pilots alike find it at times alternately satisfying and frustrating, simple and complex, safe and hazardous.

In Digest 129 the Bureau of Air Safety Investigation identifies improper landing flare as the third most significant of thirteen factors in instances where pilot factors were assigned to accidents involving private pilots.

In an age of technical precision, this critical manoeuvre remains imprecise.

This proposal discusses a practical technique for establishing a consistent flare point which does not rely on the pilot's perception of vertical height. It embraces the physical principle of motion parallax to provide a simple cue for commencement of the flare, No device or modification is required and therefore no costs are incurred. Safety is enhanced and the technique is 'pilot portable'.

Current Practice

The landing flare is one the last critical phases of flight to which the term 'seat-of-the-pants' may still be applied. The vast majority of landings, worldwide, are practiced by pilots utilising highly developed qualities of judgement, co-ordination, experience and skill.

Existing flare techniques involve a critical estimation of height above the landing surface. This is very difficult to achieve because the estimation of height and the particular height are subject to many variables, such as: Aircraft type.
Aircraft size.
Aircraft configuration.
Glide path angle.
Pilot total experience.
Pilot recent experience.
Pilot experience on type.
Pilot seating position.
Pilot performance or skill
Landing surface.
Day versus night
Visibility
Wind and turbulence.

Historically, instruction in determining a suitable and consistent flare point has been inadequate to say the least. We are attempting to recognize and extract one flare point from a range of acceptable flare circumstances. Generally, the best that instructors have been able to manage is to demonstrate a suitable flare point for a particular aircraft as being 'about here'.

The student pilot has no proper model except his memory, and that in itself is inconsistent. Trial and error are the arbiters in determining the soundness of his developing judgment. Unfortunately even after the basic skills are mastered, the problem still exists because every aircraft type requires a different flare height. as a pilot converts to successive aircraft types, he faces the same problem over and over. He has no proper model at the very time he needs one most, and there lies a clue.

Just as the student pilot consolidates his flare-height judgment, so does the experienced pilot after conversion to another aircraft type. After a time he becomes compatible with his aircraft (if he consolidates and flies it regularly), and can land it as well as any flown previously. Probably, this is a subconscious recognition of something visible to the pilot through his windshield, that is providing a usable clue for flare. Obviously, to achieve a consistency some recognition and quantification is necessary.

Vague terms such as the height of a double-decker bus, 20 feet, when the individual blades of grass are discernible, when the ground starts to 'rush', when you feel your feet are just about to reach the threshold or 'about here' are too imprecise or inconsistent and for a student they are almost incomprehensible.

We need to bring this 'something' out into the open so that we know exactly what we are looking for, what works for us, and what to use in the future.

Another way

When properly taught, pilots have little difficulty with the concept of selecting and flying an approach to a nominated aim point on the landing surface. With or without glide-slope guidance, pilots can learn to fly a consistent and stable approach angle to the aim point.

Accepting that the glide-path angle may be fixed within reasonable tolerances, it follows that any point located longitudinally on the approach path, short of the aim point, will correspond with a particular vertical height (simple triangulation).

Therefore, a flare-height of greater consistency than is possible using mere perception could be provided by a suitably chosen point along the approach path and over flown by the aircraft.

Much has been written on the subject of the aim point being the center of expansion of a flow pattern, providing the pilot with a visual illusion as points surrounding the aim point radially outwards as the aircraft approaches the ground (motion parallax).
http://members.theglobe.com/checkboard/appch1.gif

Points beyond the aim point will appear to move upward from the aim point, while points short of the aim point will appear to move downward. It is a point in this 'six o'clock' sector of the pilots view which has proven useful.

If such a point were selected and could be simply identified, a consistent longitudinal fix for the flare point for a given aircraft could be obtained as the pre selected point appeared to move down the windshield (due to increasing depression angle) to the point where it reached the lower vision or cut-off angle (limit depression angle) of the cockpit. This angle is dictated by the geometry of the pilot's seating position in relation to the aircraft structure, where, within limits, some design consistencies exist between aircraft types.

Calculation of this distance from the aim point to the flare cut-off point involves energy/geometry considerations quickly determined in practice but complicated to derive by analysis. However a suitable approximation, based on aircraft/approach geometry and thorough practical testing has provided a simple and effective alternative technique with near universal application.

The Jacobson Flare

On final approach, the aircraft occupies space vertically, in practical terms between the pilot's eye and the main wheels. Two parallel paths may be traced down the approach path: the pilot's eye path which intersects the landing surface at the aim point; and assuming, no flare, the lower mainwheel path which would intersect the landing surface at a point called the impact point.

http://members.theglobe.com/checkboard/appch2.gif

The exact formula for calculating the position of the impact point is simplified as follows:

http://members.theglobe.com/checkboard/appch4.gif

For a given aircraft type, the distance between the aim and impact points has provided suitable quantification for the flare point estimate. This distance accommodates the critical variables of glide angle, eye height above mainwheels and horizontal distance between the mainwheels and the pilot's eye - when the aircraft is on a stable approach in the landing configuration.
http://members.theglobe.com/Checkboard/APPCH3.GIF

The flare is initiated when, on a stable approach, the pre-determined impact point, appearing to move downward form the aim point. reaches the cut-off angle and disappears from view under the aircraft. In practice, it is the simplest of tasks to notice the aircraft overtake the impact point while flying an approach using standard techniques. It does not detract from the pilots attention because the point in question is on the approach centerline in the pilot's normal field of view.

The next important step is to locate the calculated impact point on the landing surface, short of the aim point. Many aviation authorities have developed runway surface markings as distance guides, often at 500, 1000 and 1500 feet form the approach threshold.

http://members.theglobe.com/checkboard/appch5.gif

Simple interpolation of these markings by the pilot satisfies the practical requirements for a visual fix along the approach axis. Where distance markers do not exist on a landing surface, the pilot can estimate the position of the impact point using variations in surface colour to texture for identification. For night operations form these surfaces, calculations based on the known distance between runway edge lights provided the pilot with a similar cue.

This flare point is extremely tolerant when compared with traditional perception techniques. For a standard 3 ° glide path, any error of judgment of flare height will, within limits, be magnified approximately 20 times, longitudinally. In marked contrast, and longitudinal inaccuracy will be reflected as only 5 percent of the figure vertically. The expanded scale of the approach axis (approximately 20 times the vertical dimension), together with a visual fix, provides a model that is visible and which provides unparalleled consistence of judgment for a student and experienced pilot alike.

Non-standard approaches

The impact point calculated for a normal approach also serves for non-standard landing configurations with their likely variations in aircraft attitude. An aircraft on approach at a higher attitude (body angle) than normal would require a higher flare point to accommodate the reduced mainwheel clearance. The higher attitude self-compensates because the lower cut-off angle is reached further back up the approach path, providing and earlier cue to flare, as would be expected. The converse also applies.

Conclusions

The technique is simple, practical and extremely effective. It was developed and tested over a period of three years in many aircraft types, ranging from single engine light aircraft to large jet transports, by civil and military pilots of varied ages, abilities and experience - and it works.

[This message has been edited by Checkboard (edited 20 December 1999).]

[Ace on Base]

Thanks Checkboard, Thats all the stuff that I have as well!

Looks very confusing, but alas, it is easy, its just as easy to teach, and it DOES WORK!!

If you have never used a system or method before, be very carefull when bagging it!! - and if you are game to try it out - CORRECTLY, it may verry well fix some of the shockers that none of you confess to..... or are you all too perfect??

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"Keep Smilin' Sunshiners!!"

[Short and Sweet]

Thanks Checkboard. That information has cleared up some of my questions. Do students seem to pick up the idea easier than the aiming point technique?

[deehav]

I agree with de la valette.

If you need all that hocus pocus to simply land an aeroplane maybe you should reconsider your position.

I have crewed with dlv as his first officer and can attest to his credentials, second to none.

Remember it is how you handle the corrections, not the initial flare, that sets the truly skillful operator apart.

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[Checkboard]

deehav, while I agree that it seems the only people who spend this much time and effort making 'simple' things like landing appear complicated are those that have trouble with them, you have to remember that this isn't a "flying tips for skillful operators" forum, but an "Instructor" forum.

Instructors run into people that have trouble with some aspect of flying everyday - that is what instructors do. Having another arrow in your quiver when teaching an aspect of flying is what makes a professional instructor.

As to the "Jacobson Flare" - I didn't bother with it unless a student was having trouble with round-out height. In that case I would explain the technique, and I usually found that the change in explaination, or the different way of looking at things out of the window would fix the problem.

deehav - if you are a whip at everything aviation, then all power to you - go and enlighten us all in "Tech". If you have never instructed, or have instructed but have never had a student struggle, then you have little to add here.

P.S. Sorry about the flame, but it is my firm belief that anybody that can obtain a car licence should be able to obtain a PPL, if their instructor is good enough, and they have a firm desire to succeed.

Nothing annoys me more than an instructor that has an attitude of "Landing is easy! If you can't simply land an aeroplane maybe you should reconsider your position."

[This message has been edited by Checkboard (edited 22 December 1999).]

[Tips]

It is interesting to note that if you take all the letters of "Jacobsons Flare", rearrange them, add a few and take a few others away you come up with "What a total waste of time, let us re reinvent the wheel again."

[Tinstaafl]

I understand the concept - after all,it's only triangles, and distance along a runway is easier to perceive while approaching than height above it.

But how does one determine the 'proper' distance prior to the aim point from which to commence the flare?

I used to have the maths describing the Jacobson flare technique but never used it in anger. Sort of read it with passing interest but don't remember / missed the point about how to find this required distance.

[This message has been edited by Tinstaafl (edited 23 December 1999).]

[deehav]

Dear checkboard,
I think you missunderstood my reply.
I got the impression that it is the flare height and the arrival that is helped by JF.
Not all flares and touchdowns are linear in there execution, there is an amount of juggling to be done.
The ability to judge height and recorrect if needed is what the instructor is looking for.
You cannot send a student solo if they can't bracket during the arrival.
You question my experience, unfortunately I am considered to be a bit of a dinosaur.It comes with age and dare I say it, experience.
These days I only instruct on DH-82 and DHC-1 if I wish to find the time.

[de La Valette]

Checkerboard. I think you need to sit down and have a nice cup of tea, because you are getting a bit tetchy and resorting to sarcasm. Deehav made a perfectly good point as far as the general application of the Jacobson flare is concerned. His post said "Remember it is how you handle the corrections, not the initial flare, that sets the truly skillful operators apart."

I would agree entirely with deehav. The flare is rarely the problem. It is the gyrations after the flare ie drift, balloon,yaw etc, that causes most concern with ab-initio students. Certainly you should not have to resort to statements of mathematical angles to teach someone when to flare in a C150. Just quietly say, "Watch how I do it, Bloggs and follow me through please" As someone said in an earlier post, students have learnt to land au natural since flight began.

[4dogs]

DLV,

"The flare is rarely the problem. It is the gyrations after the flare ie drift, balloon,yaw etc, that causes most concern with ab-initio students. Certainly you should not have to resort to statements of mathematical angles to teach someone when to flare in a C150. Just quietly say, "Watch how I do it, Bloggs and follow me through please" As someone said in an earlier post, students have learnt to land au natural since flight began."

Gee whizz! I had almost forgotten about the "observational osmosis" theory of flight instruction. It is just a little easier than learning the "piano by ear" or taking the Spartan approach to survival training!

Actually, Checkers (who was already residing high in my regard) has elevated himself further - he faithfully reported something in which others had shown interest and demonstrated sgnificant maturity by passing on how he fitted the Jacobsen Flare into his instructional toolkit. He neither denigrated nor exaggerated, he merely acknowledged variety and utility. His reward? "Sit down and have a cup of tea"??? Shame on both your houses!

I have just been through an exercise where I had to revisit what I used to do quite "naturally", ie without conscious thought or analysis. I had some difficulty remembering how I did it, what cues I used, what control movements I used and most importantly what trade-offs I used. Certainly, I could have invited someone to "follow me through" without explanation, but then they would have been trying to emulate my thought processes as well as my physical manipulations without understanding. The few instructional successes that I have had (in 21 years of trying to do it better) have occurred when I have been able to explain the mechanics of what I am doing, the thought processes behind what I am doing and the ways that I occasionally modify the processes according to what I see. Jacobsen attempted to do that and, while I am personally ambivalent, has developed a significant following. In short, the technique/explanation/call it what you will has produced the goods for a lot of people - it seems to have earnt the right to survive.

Perhaps you and deehav should share a "Bex and a good lie down" while the rest of us recognise the balance in Checker's intentions, if not in his "watch me and follow me through".


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Stay Alive,

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